i66 



COFFEE 



in Peruvian guano and leguminous seedlings ; adenine, found in the 

 leaves of Thea sinensis L., and in the root of Beta vulgaris L. ; and 

 vernine, a pentoside of adenine, found in Vicia seedlings. These sub- 

 stances are all derivatives of the same base, purine. Purine is also 

 the mother substance of a number of compounds present in animals, 

 such as uric acid, methyl- and dimethyl-xanthine, methyl-guanine, etc. 

 The relationship of the members of this group to the mother substance 

 and to each other is best noted from a consideration of their constitu- 

 tional formulae. 



Purine. 

 ,N==eCH 



CH 5C- 



:N- 



.0 



-7NH 



or purine, written in the following form, shows clearly that it con- 

 sists of two rings; the upper six-membered pyramidal ring; and the 

 lower five-membered imidazol or gly-oxaline ring. 



2CH N^ 



/ \ 



/ \ 



3N eCH 



\ / 



4^ L/5 



,N 



\ 



7NH 



\ / 

 gCH 



Xanthine or 2 : 6 dioxypurine. 

 NH CO 



CO 



NH- 



-C- 



-NH 

 >CH 



-N 



This formula indicates that xanthine may be regarded as purine plus 



